Manufacturers of injection-molded parts have an ongoing need to make a wide range of parts in a highly efficient and cost-effective manner. Increasingly, there is a need to provide composite part assemblies made up of plural component parts. These composite part assemblies frequently require movement by one or more of the component parts. Representative composite part assemblies which include movable parts are closures of the type used for packaging of food and personal care products.
Manufacture of composite part assemblies may require separate forming and assembly steps in which the component parts are first formed in the mold and then assembled to make the finished product. Separate forming and assembly steps can decrease throughput and increase the cost of the finished product.
One approach toward improving the efficiency of manufacturing composite parts is referred to by some as in-mold assembly. In-mold assembly refers to the forming of one or more parts followed by assembly of the parts before ejection from the mold. Various approaches to in-mold assembly have been proposed. Examples include: U.S. Patent Publication Nos. 2006/0033238 (Gram), 2004/0033287 (Gram) and 2004/0119200 (Gram) and U.S. Pat. Nos. 4,744,741 (Glover et al.) and 4,330,257 (Rees et al.). These approaches have certain disadvantages and limitations associated with them.
For example, the process described in Publication No. 2006/0033238 relates to production of hinged-together plastic objects. After part formation, a closing mechanism works in combination with a rotating tool to partially close one portion of the hinged part while a portion of the hinged part remains in the tool. This process lacks the capability of assembling a finished part consisting of separate plural parts.
The process described in Publication No. 2004/0033287 relates to forming and assembly of at least two part objects. Separate parts are formed in separate rotating tools. After forming, the part edge surfaces are heated and the rotating tools are moved together so that the heated edge surfaces touch and are thermally bonded together. This process has limitations in that thermal joining of parts may not be satisfactory for certain other types of manufacturing processes.
U.S. Pat. No. 4,744,741 describes a process for simultaneous forming and assembly of plural-part molded objects. This process requires thermal bonding of the parts immediately following forming and may be subject to unduly long cycle times because coordinated movement of separate tools is required to assemble the parts.
U.S. Pat. No. 4,330,257 describes a process for efficient forming of molded parts using a rotating tool but does not provide for assembly of the parts.
It would represent a significant improvement in the art to provide a method and apparatus for molding and assembling of plural-part plastic assemblies which would facilitate the manufacture of plural-part assemblies, which would facilitate manufacture of assemblies including one or more moving parts, which would increase throughput and decrease production cycle times and which would be efficient and cost-effective to implement.